The advancement in the field of material science has gifted us new electrically conductive materials having good mechanical properties and thermal characteristics. Machining these materials using conventional machining process is a challenging task. Electrical discharge machining (EDM) is a well-established machining process used to manufacture process hard materials having geometrically complex shapes, that are extremely difficult to machine traditionally. EDM is a thermo-electric process in which material is eroded by rapidly recurring sparks between the non-contacted electrode and workpiece. As there is no direct contact between the electrodes in EDM, machining defects like mechanical stresses, clattering & vibration do not create problems during machining. In spite of the advantages of the process, its use in industry is limited owing to poor surface finish and low volumetric material removal. To overcome these drawbacks, the metallic powder is mixed in the dielectric fluid, which increases its conductive strength and increases the spark gap distance between the tool and workpiece. This new evolved material removal process is called Powder Mixed Electrical Discharge Machining (PMEDM). The added powder significantly affects the performance of the EDM process. The objective of this review is to benefit the researchers to understand the PMEDM concept precisely and study the process parameters furthermore in particulars to get enhancements in the process to achieve better quality levels.

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In the present work, surface characteristics of powder mixed electro-discharge machining (PMEDM) process are investigated using alumina and carborundum abrasive powder added dielectric fluid for titanium alloy Ti6Al4V. Deionized water is utilized as dielectric to accomplish an environmentally safe machining climate, and limit the emanation of harmful substances. Pulse ON/OFF time (TON/TOFF), discharge current (IP), and powder concentration (PC) are selected as process variables to reconnoiter characteristics of performance like surface finish, rate of material removal, and tool wear. The multi-response optimization has been performed using grey relational analysis (GRA) to establish the optimal parametric combination of process variables that gives the finest surface quality and minutest tool wear. The investigation results divulge that discharge current (IP) and powder concentration (PC) have the most significant effect on material removal rate (MRR), tool wear rate (TWR), and surface finish. The surface characteristics were evaluated by scanning electron microscope for the optimal parameters combination. The minutest value of surface roughness and tool wear rate is achieved at IP: 06 amps, TON: 05 µS, TOFF: 96 µS, and PC: 0.50 g/L. The optimized set of parameters would help process engineers to attain improved machining performance of PMEDM, economically along with desired surface characteristics.

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